1. Field of the Invention
The present invention relates to a semiconductor integrated circuit device suitable for a receiver which receives video information by performing inter-equipment authentication.
2. Description of the Related Art
The digitization of video information, audio information and the like (hereinafter referred to as AV information) has hitherto been pushed forward with. Digital broadcasting, such as BS digital television broadcasting and digital terrestrial television broadcasting, has also been started, and digitized AV information (AV data) has come to be broadcast as digital contents. DVD recorders, hard disk recorders, semiconductor memory recorders and the like have also come into widespread use as devices which record such digital AV data.
In digital recording, it is possible to prepare replicates without degrading original AV data and from the viewpoint of the protection of copyrights, the necessity for limiting the copying of digital contents has been increasing. In consideration of such a function of protecting copyrights and transmission for high image quality and of the handling of cables as well, the HDMI (high-definition multimedia interface) has come to be adopted which transmits uncompressed video signals via one cable and also transmits audio signals and control signals. It should be noted that the HDMI is disclosed in Japanese Patent Application Laid-Open Publication No. 2007-108198, for example.
In the HDMI, TMDS (transition minimized differential signaling) is adopted which is a standard for transmission in physical layers. Also, in the HDMI, the DDC (display data channel) is adopted in order to cause source equipment, such as recording apparatus, to automatically recognize various kinds of electrical specifications and the like for displays. In this DDC, two-wire serial transmission of the I2C (I squared C) bus type is adopted. And the EDID (extended display identification data) standard is adopted as a standard for electrical specifications and the like for the automatic recognition in which this DDC is used.
An HDMI receiver which receives signals from source equipment, such as digital recording apparatus, is provided with an EDID section for inter-equipment authentication in addition to a data authentication section which receives TMDS signals. The EDID section deals with EDID information for checking the performance, function and the like of receiver equipment such as display devices.
In recent years, with the number of pieces of source equipment which produces outputs compatible with HDMI increasing, receiver equipment, such as digital television receivers, provided with a plurality of HDMI ports has become widespread. In such receiver equipment, an EDID section is provided for each HMDI port, thereby enabling EDID information to be transmitted to source equipment corresponding to each HDMI port.
In general, an E2 PROM which stores EDID information is adopted as an EDID section. Therefore, when a plurality of HDMI ports are provided, it is necessary to prepare a plurality of E2 PROMs constituting the EDID section and to provide a changeover switch for selecting one of the plurality of E2 PROMs. In such a system provided with a plurality of E2 PROMs, from the standpoints of the miniaturization of the device, low power consumption and the like, it is advantageous to integrate the plurality of E2 PROMs and to form a plurality of EDID sections corresponding to a plurality of HDMI ports on one LSI. Hence, systems in which a data authentication section and an EDID section are incorporated on an SoC (a system on chip) constituting a digital television receiver have been developed.
However, the EDID section is intended to permit inter-equipment authentication by transmitting EDID information to source equipment via the DDC, and it is necessary that operation be possible during access from the source equipment. For this reason, it is necessary that power be constantly supplied to the EDID section during access from the source equipment irrespective of the operating condition, such as an on condition and an off condition, of the receiver equipment. That is, when the SoC design of the EDID section is adopted, it is necessary that power be constantly supplied to the SoC in order to supply power to the EDID section, and power consumption increases.